1. Field of the Invention
The present invention relates to an automatic stop device and method for an internal combustion engine, and particularly to a technique of automatically stopping the internal combustion engine coupled to a transmission through a frictional engagement element brought into a released state by a driver's operation.
2. Description of the Background Art
There has conventionally been known a vehicle having a manual transmission (hereinafter also referred to as an MT) mounted thereon. In the MT, a clutch is brought into a released state or an engaged state by the operation of a clutch pedal. An operation of such an MT vehicle is burdensome in performing a hill-start or in low-speed running, and is difficult for an inexperienced driver. Accordingly, there has been proposed a technique of bringing a clutch into a released state or an engaged state independently of the operation of a clutch pedal.
Japanese Utility Model Laying-Open No. 05-014664 discloses a vehicle clutch device capable of reducing the burden of operating a clutch pedal. The vehicle clutch device described in Japanese Utility Model Laying-Open No. 05-014664 is a vehicle clutch device configured to transfer engine output torque to a transmission through a friction clutch, and to allow the clutch to be released by working hydraulic pressure generated by the operation of the clutch pedal. The vehicle clutch device includes a hydraulic pump generating working hydraulic pressure for release independently of the operation of the clutch pedal, an engine rotation speed detecting unit detecting a rotation speed of an engine, a vehicle speed detecting unit detecting a running speed of the vehicle, an accelerator pedal operated amount detecting unit detecting an operated amount of the accelerator pedal, and a hydraulic pressure control unit controlling the working hydraulic pressure for release generated by the hydraulic pump, based on the detected rotation speed of the engine, running speed of the vehicle, and operated amount of the accelerator pedal.
According to the vehicle clutch device described in the publication, the device is provided with a hydraulic pump that generates working hydraulic pressure for releasing the clutch independently of the clutch pedal, and the working hydraulic pressure for releasing the clutch, which working hydraulic pressure is generated by the hydraulic pump, is controlled based on the rotation speed of the engine, running speed of the vehicle, and operated amount of the accelerator pedal. Accordingly, when the clutch is required to be engaged and released in a repeated manner in a congested route and the like, it is possible to reduce the burden of the driver operating the clutch pedal.
In recent years, owing to increased awareness of environmental issues, more fuel-efficient vehicles are demanded. As a method of improving fuel efficiency of the vehicle, there has been known a technique called idle stop (which is also referred to as economy running or eco-run) with which an engine is automatically stopped when a vehicle temporarily stops at a red light and the like. However, Japanese Utility Model Laying-Open No. 05-014664 does not describe that idle stop is performed in a suitable manner in a vehicle where a clutch is engaged or released independently of the clutch pedal.